Cygwin gcc - asm错误： [英] Cygwin gcc - asm error:

问题描述

我有一个用C编写的项目，最初是在Linux上完成的，但现在必须在Windows上完成。部分代码在几个地方包含此行

I have a project written in C that originally was being done on Linux, but now must be done on Windows. Part of the code include this line in several places

asm("movl temp, %esp");

但是这会导致未定义引用`temp'错误。

But that causes an "undefined reference to `temp'" error.

在Linux上使用gcc 4.3.2编译器（在另一台机器上测试）编译没有问题，这是我在Cygwin上的版本。

This has no problem compiling on Linux using the gcc 4.3.2 compiler (tested on another machine), which is the version I have on Cygwin. Is there another way to accomplish what this line is doing?

推荐答案

您需要从

asm("movl temp, %esp");

到

asm("movl _temp, %esp");

是的，它是相同的编译器和汇编程序，但是它们的设置方式与主机系统兼容。

Yes, it's the same compiler and assembler but they are set up differently for compatibility with the host system.

您可以通过简单地告诉gcc使用特定的名称来隔离系统相关的符号前缀：

You can isolate the system-dependent symbol prefixing by simply telling gcc a specific name to use:

int *temp asm("localname");
...
__asm__("movl localname,%esp");

这避免了某种类型的#if，并删除了主机操作系统依赖，但添加了一个编译器依赖。说到编译器扩展，有些人会写（例如 info as ）：

This avoids an #if of some sort and removes a host OS dependency but adds a compiler dependency. Speaking of compiler extensions, some people would write (see info as) something like:

#ifdef __GNUC__
    __asm__("movl %[newbase],%%esp"
                :
                : [newbase] "r,m" (temp)
                : "%esp");
#else
#error haven't written this yet
#endif

这里的想法是，这种语法允许编译器帮助你，通过找到 temp ，即使它在说谎在寄存器或需要几个指令加载，还要避免与你冲突，它的情况下，它是使用一个注册你破烂。它需要这个，因为一个简单的 __ asm __（）不以任何方式被编译器解析。

The idea here is that this syntax allows the compiler to help you out, by finding temp, even if it's lying about in a register or takes a few instructions to load, and also to avoid conflicting with you, it case it was using a register you clobbered. It needs this because a plain __asm__() is not parsed in any way by the compiler.

，你似乎正在实现自己的线程包，所以没有一个真的很重要。 Gcc不打算使用％esp进行计算。 （但为什么不使用pthreads ...？）

In your case, you seem to be implementing your own threading package, and so none of this really matters. Gcc wasn't about to use %esp for a calculation. (But why not just use pthreads...?)

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